#Solution 1: Manual Uploading/Tracking to Files.app
If you want to stick to iCloud Drive and achieve the this, you'll need to manually upload your photos to iCloud using **Photos -> Select -> (Select Photos) -> Share -> Save to Files**

In this method you'll have to manually keep track of the photos you've uploaded and the new ones that haven't been uploaded yet.

#Solution 2: Google Photos for iOS
Google photos app for iOS brings the same 

> Free Photo and Video Storage

feature for iOS, which were initially advertised with the Google Pixel.

**Note: Google Photos will automatically reduce your photo quality if you use the free plan.**

In this method, the app handles the sync history and keeps track of the backup metadata for you, so you won't have to worry about uploading new photos manually.

[App Store: Google Photos][1]


  [1]: https://itunes.apple.com/us/app/google-photos/id962194608?mt=8